This invention relates to the field of circuit elements. More particularly, this invention relates to a method of providing through-holes through circuit elements so as to connect a rigid or hard circuit element to a flexible circuit element, the circuit elements being connected at the through-holes.
A typical procedure for providing a through-hole passage through a plurality of circuit elements generally includes the formation of corresponding holes through which the elements may be connected. Thereafter, the plural circuit elements are electrically connected at the through-hole passage via a nonelectrolytic plating procedure followed by an electrolytic plating procedure whereby the passage is thickened. However, when one of the circuit elements is a flexible circuit element, material from the nonelectrolytic plating treatment may be deposited uniformly to the circuit pattern and/or part of the substrate of the flexible circuit in the vicinity of the through-hole. As a result, the flexibility of the flexible circuit may be adversely decreased. In order to avoid this undesirable decrease in flexibility, the electroplated layer must be removed from the flexible circuitry layer after the nonelectrolytic plating treatment to thereby leave only the through-hole passageway coated. Unfortunately, it will be appreciated that the conventional method for removing such a coating from flexible circuit substrates is generally complex. Moreover, there is danger that the circuit pattern will be damaged during this removal process. Thus, the prior art method of electrically connecting flexible and rigid circuit elements at a through-hole has many problems from at least the standpoints of cost and reliability.